<!DOCTYPE html>
<meta charset="utf-8">
<title>ScrollTimeline current time algorithm - root scroller</title>
<link rel="help" href="https://wicg.github.io/scroll-animations/#current-time-algorithm">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/web-animations/testcommon.js"></script>

<style>
html {
  /* Ensure the document is scrollable. */
  min-height: 100%;
  min-width: 100%;
  padding-bottom: 100px;
  padding-right: 100px;
}
</style>

<script>
promise_test(async t => {
  const scroller = document.scrollingElement;
  // Set the timeRange(s) such that currentTime maps directly to the value
  // scrolled. This makes it easier to assert on the currentTime in the test.
  const scrollerHeight = scroller.scrollHeight - scroller.clientHeight;
  const scrollerWidth = scroller.scrollWidth - scroller.clientWidth;

  const blockScrollTimeline = new ScrollTimeline(
      { scrollSource: scroller, timeRange: scrollerHeight, orientation: 'block' });
  const inlineScrollTimeline = new ScrollTimeline(
      { scrollSource: scroller, timeRange: scrollerWidth, orientation: 'inline' });

  // Unscrolled, both timelines should read a currentTime of 0.
  assert_equals(blockScrollTimeline.currentTime, 0);
  assert_equals(inlineScrollTimeline.currentTime, 0);

  // Now do some scrolling and make sure that the ScrollTimelines update.
  scroller.scrollTop = 50;
  scroller.scrollLeft = 75;
  // Wait for new animation frame  which allows the timeline to compute new
  // current time.
  await waitForNextFrame();

  // As noted above, the timeRange(s) are mapped such that currentTime should be
  // the scroll offset.
  assert_equals(blockScrollTimeline.currentTime, 50);
  assert_equals(inlineScrollTimeline.currentTime, 75);
}, 'currentTime calculates the correct time for a document.scrollingElement scrollSource');
</script>
